Cadbury launched Wispa Duo bar, two smaller bars in one pack, earlier this month. The bar has a retail price of 68p, which is 18p more expensive than a regular Wispa.
The light-hearted campaign, created by Fallon, will ask consumers whether they prefer the right or the left of the two bars.
The campaign comprises a mix of outdoor and targeted online activity, starting from Monday.
Additionally, consumers can also go to the Wispa Facebook page to let other Wispa fans know which side bar they favour and to find out if others agree.
Ross Farquhar, brand manager for Cadbury Wispa, says: "The launch of Wispa Duo is an exciting moment for Cadbury Wispa. Consumers have been crying out their beloved Wispa in more formats, and we're delighted to give it to them.
"It's a bar of two halves, but which do you prefer? Personally, I prefer the left bar. It's just more...leftie."
.jpg)
.jpg)